example.js

var loadImage = require('image').loadImage;

var images = [
  'url1',
  'url2',
  'url3',
  //...
];

Promise.all(images.map(loadImage)).then(function() {
  console.log("All images have been loaded");
});

example2.js

var images = [];

$('image').each(function(el) {
  images.append(new Promise(function(resolve, reject) {
    el.onload = function() {
      resolve();
    };
  }));
});

Promises.all(images).then(function() {
  console.log("all images are loaded");
});

image.js

module.exports = {
  loadImage: function(url) {
    return new Promise(function(resolve, reject) {
      var img = new Image();
      
      img.onload = function() {
        resolve(url);
      };
      
      img.onerror = function() {
        reject(url);
      };
      
      img.src = url;
    });
  }
}